Package com.puppycrawl.tools.checkstyle.checks.coding

Class HiddenFieldCheck

java.lang.Object
com.puppycrawl.tools.checkstyle.api.AutomaticBean
com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
com.puppycrawl.tools.checkstyle.api.AbstractCheck
com.puppycrawl.tools.checkstyle.checks.coding.HiddenFieldCheck
All Implemented Interfaces:
Configurable, Contextualizable
public class HiddenFieldCheck extends AbstractCheck

Checks that a local variable or a parameter does not shadow a field that is defined in the same class.

It is possible to configure the check to ignore all property setter methods.

A method is recognized as a setter if it is in the following form 

 ${returnType} set${Name}(${anyType} ${name}) { ... }

where ${anyType} is any primitive type, class or interface name; ${name} is name of the variable that is being set and ${Name} its capitalized form that appears in the method name. By default it is expected that setter returns void, i.e. ${returnType} is 'void'. For example 

 void setTime(long time) { ... }

Any other return types will not let method match a setter pattern. However, by setting setterCanReturnItsClass property to true definition of a setter is expanded, so that setter return type can also be a class in which setter is declared. For example 

 class PageBuilder {
   PageBuilder setName(String name) { ... }
 }

Such methods are known as chain-setters and a common when Builder-pattern is used. Property setterCanReturnItsClass has effect only if ignoreSetter is set to true.

  • Property ignoreFormat - Define the RegExp for names of variables and parameters to ignore. Type is java.util.regex.Pattern. Default value is null.
  • Property ignoreConstructorParameter - Control whether to ignore constructor parameters. Type is boolean. Default value is false.
  • Property ignoreSetter - Allow to ignore the parameter of a property setter method. Type is boolean. Default value is false.
  • Property setterCanReturnItsClass - Allow to expand the definition of a setter method to include methods that return the class' instance. Type is boolean. Default value is false.
  • Property ignoreAbstractMethods - Control whether to ignore parameters of abstract methods. Type is boolean. Default value is false.
  • Property tokens - tokens to check Type is java.lang.String[]. Validation type is tokenSet. Default value is: VARIABLE_DEF, PARAMETER_DEF, PATTERN_VARIABLE_DEF, LAMBDA, RECORD_COMPONENT_DEF.

To configure the check: 

  <module name="HiddenField"/>
 
 public class SomeClass {

   private String field;
   private String testField;

   public SomeClass(String testField) { // violation, 'testField' param hides 'testField' field
   }
   public void method(String param) { // OK
       String field = param; // violation, 'field' variable hides 'field' field
   }
   public void setTestField(String testField) { // violation, 'testField' param
                                                // hides 'testField' field
       this.field = field;
   }
   public SomeClass setField(String field) { // violation, 'field' param hides 'field' field
       this.field = field;
   }
 }

To configure the check so that it checks local variables but not parameters: 

 <module name="HiddenField">
   <property name="tokens" value="VARIABLE_DEF"/>
 </module>
 
 public class SomeClass {

   private String field;
   private String testField;

   public SomeClass(String testField) { // OK, 'testField' param doesn't hide any field
   }
   public void method(String param) { // OK
       String field = param; // violation, 'field' variable hides 'field' field
   }
   public void setTestField(String testField) { // OK, 'testField' param doesn't hide any field
       this.field = field;
   }
   public SomeClass setField(String field) { // OK, 'field' param doesn't hide any field
       this.field = field;
   }
 }

To configure the check so that it ignores the variables and parameters named "test": 

 <module name="HiddenField">
   <property name="ignoreFormat" value="^testField"/>
 </module>
 
 public class SomeClass {

   private String field;
   private String testField;

   public SomeClass(String testField) { // OK, because it match ignoreFormat
   }
   public void method(String param) { // OK
       String field = param; // violation, 'field' variable hides 'field' field
   }
   public void setTestField(String testField) { // OK, because it match ignoreFormat
       this.field = field;
   }
   public SomeClass setField(String field) { // violation, 'field' param hides 'field' field
       this.field = field;
   }
 }

To configure the check so that it ignores constructor parameters: 

 <module name="HiddenField">
   <property name="ignoreConstructorParameter" value="true"/>
 </module>
 
 public class SomeClass {

   private String field;
   private String testField;

   public SomeClass(String testField) { // OK, 'testField' param doesn't hide any field
   }
   public void method(String param) { // OK
       String field = param; // violation, 'field' variable hides 'field' field
   }
   public void setTestField(String testField) { // violation, 'testField' variable
                                                // hides 'testField' field
       this.field = field;
   }
   public SomeClass setField(String field) { // violation, 'field' param hides 'field' field
       this.field = field;
   }
 }

To configure the check so that it ignores the parameter of setter methods: 

 <module name="HiddenField">
   <property name="ignoreSetter" value="true"/>
 </module>
 
 public class SomeClass {

   private String field;
   private String testField;

   public SomeClass(String testField) { // violation, 'testField' param hides 'testField' field
   }
   public void method(String param) { // OK
       String field = param; // violation, 'field' variable hides 'field' field
   }
   public void setTestField(String testField) { // OK, 'testField' param doesn't hide any field
       this.field = field;
   }
   public SomeClass setField(String field) { // violation, 'field' param hides 'field' field
       this.field = field;
   }
 }

To configure the check so that it ignores the parameter of setter methods recognizing setter as returning either void or a class in which it is declared: 

 <module name="HiddenField">
   <property name="ignoreSetter" value="true"/>
   <property name="setterCanReturnItsClass" value="true"/>
 </module>
 
 public class SomeClass {

   private String field;
   private String testField;

   public SomeClass(String testField) { // violation, 'testField' param hides 'testField' field
   }
   public void method(String param) { // OK
       String field = param; // violation, 'field' variable hides 'field' field
   }
   public void setTestField(String testField) { // OK, 'testField' param doesn't hide any field
       this.field = field;
   }
   public SomeClass setField(String field) { // OK, 'field' param doesn't hide any field
       this.field = field;
   }
 }

To configure the check so that it ignores parameters of abstract methods: 

 <module name="HiddenField">
   <property name="ignoreAbstractMethods" value="true"/>
 </module>
 
 abstract class SomeClass {

   private String field;

   public SomeClass(int field) { // violation, 'field' param hides a 'field' field
     float field; // violation, 'field' variable hides a 'field' field
   }
   public abstract int method(String field); // OK
 }

 public class Demo extends SomeClass {

   public int method(String param){
     return param;
   }
 }

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

  • hidden.field
Since:
3.0

  • Field Details

    • MSG_KEY

      public static final String MSG_KEY
      A key is pointing to the warning message text in "messages.properties" file.
      See Also:

    • frame

      private HiddenFieldCheck.FieldFrame frame
      Stack of sets of field names, one for each class of a set of nested classes.

    • ignoreFormat

      private Pattern ignoreFormat
      Define the RegExp for names of variables and parameters to ignore.

    • ignoreSetter

      private boolean ignoreSetter
      Allow to ignore the parameter of a property setter method.

    • setterCanReturnItsClass

      private boolean setterCanReturnItsClass
      Allow to expand the definition of a setter method to include methods that return the class' instance.

    • ignoreConstructorParameter

      private boolean ignoreConstructorParameter
      Control whether to ignore constructor parameters.

    • ignoreAbstractMethods

      private boolean ignoreAbstractMethods
      Control whether to ignore parameters of abstract methods.

  • Constructor Details

    • HiddenFieldCheck

      public HiddenFieldCheck()

  • Method Details

    • getDefaultTokens

      public int[] getDefaultTokens()
      Description copied from class: AbstractCheck
      Returns the default token a check is interested in. Only used if the configuration for a check does not define the tokens.
      Specified by:
      getDefaultTokens in class AbstractCheck
      Returns:
      the default tokens
      See Also:

    • getAcceptableTokens

      public int[] getAcceptableTokens()
      Description copied from class: AbstractCheck
      The configurable token set. Used to protect Checks against malicious users who specify an unacceptable token set in the configuration file. The default implementation returns the check's default tokens.
      Specified by:
      getAcceptableTokens in class AbstractCheck
      Returns:
      the token set this check is designed for.
      See Also:

    • getRequiredTokens

      public int[] getRequiredTokens()
      Description copied from class: AbstractCheck
      The tokens that this check must be registered for.
      Specified by:
      getRequiredTokens in class AbstractCheck
      Returns:
      the token set this must be registered for.
      See Also:

    • beginTree

      public void beginTree(DetailAST rootAST)
      Description copied from class: AbstractCheck
      Called before the starting to process a tree. Ideal place to initialize information that is to be collected whilst processing a tree.
      Overrides:
      beginTree in class AbstractCheck
      Parameters:
      rootAST - the root of the tree

    • visitToken

      public void visitToken(DetailAST ast)
      Description copied from class: AbstractCheck
      Called to process a token.
      Overrides:
      visitToken in class AbstractCheck
      Parameters:
      ast - the token to process

    • processLambda

      private void processLambda(DetailAST ast)
      Process a lambda token. Checks whether a lambda parameter shadows a field. Note, that when parameter of lambda expression is untyped, ANTLR parses the parameter as an identifier.
      Parameters:
      ast - the lambda token.

    • visitOtherTokens

      private void visitOtherTokens(DetailAST ast, int type)
      Called to process tokens other than TokenTypes.VARIABLE_DEF and TokenTypes.PARAMETER_DEF.
      Parameters:
      ast - token to process
      type - type of the token

    • leaveToken

      public void leaveToken(DetailAST ast)
      Description copied from class: AbstractCheck
      Called after all the child nodes have been process.
      Overrides:
      leaveToken in class AbstractCheck
      Parameters:
      ast - the token leaving

    • processVariable

      private void processVariable(DetailAST ast)
      Process a variable token. Check whether a local variable or parameter shadows a field. Store a field for later comparison with local variables and parameters.
      Parameters:
      ast - the variable token.

    • isIgnoredParam

      private boolean isIgnoredParam(DetailAST ast, String name)
      Checks whether method or constructor parameter is ignored.
      Parameters:
      ast - the parameter token.
      name - the parameter name.
      Returns:
      true if parameter is ignored.

    • isInstanceField

      private boolean isInstanceField(DetailAST ast, String name)
      Check for instance field.
      Parameters:
      ast - token
      name - identifier of token
      Returns:
      true if instance field

    • isMatchingRegexp

      private boolean isMatchingRegexp(String name)
      Check name by regExp.
      Parameters:
      name - string value to check
      Returns:
      true is regexp is matching

    • isInStatic

      private static boolean isInStatic(DetailAST ast)
      Determines whether an AST node is in a static method or static initializer.
      Parameters:
      ast - the node to check.
      Returns:
      true if ast is in a static method or a static block;

    • isIgnoredSetterParam

      private boolean isIgnoredSetterParam(DetailAST ast, String name)
      Decides whether to ignore an AST node that is the parameter of a setter method, where the property setter method for field 'xyz' has name 'setXyz', one parameter named 'xyz', and return type void (default behavior) or return type is name of the class in which such method is declared (allowed only if setSetterCanReturnItsClass(boolean) is called with value true).
      Parameters:
      ast - the AST to check.
      name - the name of ast.
      Returns:
      true if ast should be ignored because check property ignoreSetter is true and ast is the parameter of a setter method.

    • isSetterMethod

      private boolean isSetterMethod(DetailAST aMethodAST, String aName)
      Determine if a specific method identified by methodAST and a single variable name aName is a setter. This recognition partially depends on mSetterCanReturnItsClass property.
      Parameters:
      aMethodAST - AST corresponding to a method call
      aName - name of single parameter of this method.
      Returns:
      true of false indicating of method is a setter or not.

    • capitalize

      private static String capitalize(String name)
      Capitalizes a given property name the way we expect to see it in a setter name.
      Parameters:
      name - a property name
      Returns:
      capitalized property name

    • isIgnoredConstructorParam

      private boolean isIgnoredConstructorParam(DetailAST ast)
      Decides whether to ignore an AST node that is the parameter of a constructor.
      Parameters:
      ast - the AST to check.
      Returns:
      true if ast should be ignored because check property ignoreConstructorParameter is true and ast is a constructor parameter.

    • isIgnoredParamOfAbstractMethod

      private boolean isIgnoredParamOfAbstractMethod(DetailAST ast)
      Decides whether to ignore an AST node that is the parameter of an abstract method.
      Parameters:
      ast - the AST to check.
      Returns:
      true if ast should be ignored because check property ignoreAbstractMethods is true and ast is a parameter of abstract methods.

    • setIgnoreFormat

      public void setIgnoreFormat(Pattern pattern)
      Setter to define the RegExp for names of variables and parameters to ignore.
      Parameters:
      pattern - a pattern.

    • setIgnoreSetter

      public void setIgnoreSetter(boolean ignoreSetter)
      Setter to allow to ignore the parameter of a property setter method.
      Parameters:
      ignoreSetter - decide whether to ignore the parameter of a property setter method.

    • setSetterCanReturnItsClass

      public void setSetterCanReturnItsClass(boolean aSetterCanReturnItsClass)
      Setter to allow to expand the definition of a setter method to include methods that return the class' instance.
      Parameters:
      aSetterCanReturnItsClass - if true then setter can return either void or class in which it is declared. If false then in order to be recognized as setter method (otherwise already recognized as a setter) must return void. Later is the default behavior.

    • setIgnoreConstructorParameter

      public void setIgnoreConstructorParameter(boolean ignoreConstructorParameter)
      Setter to control whether to ignore constructor parameters.
      Parameters:
      ignoreConstructorParameter - decide whether to ignore constructor parameters.

    • setIgnoreAbstractMethods

      public void setIgnoreAbstractMethods(boolean ignoreAbstractMethods)
      Setter to control whether to ignore parameters of abstract methods.
      Parameters:
      ignoreAbstractMethods - decide whether to ignore parameters of abstract methods.